Thermosetting resin composition

ABSTRACT

A resin composition including at least (A) an epoxy resin, (B) a curing agent and (C) an inorganic filler, satisfies the following conditions:
         (I-I) the minimum modulus is no greater than 10 4  MPa when evaluated at a set temperature of 200° C. after temperature increase from room temperature to 200° C. at 50° C./min by evaluation with a rheometer, and the final modulus is 10 5  MPa or greater from 10 minutes after the initial temperature increase;   (I-II) the softening point of the epoxy resin (A) is 35° C. or higher;   (I-III) the residual solvent in the resin composition is no greater than 0.1%; and   (I-IV) the equivalent value of the curing agent (B) is no greater than 90 g/eq and the softening point is 105° C. or higher.

TECHNICAL FIELD

The present invention relates to a thermosetting resin composition thathas excellent heat resistance when cured, to a sealing material usingthe curable resin composition, to a semiconductor device using thesealing material, and to a production method in which the semiconductordevice is sealed.

BACKGROUND ART

Epoxy resin compositions are thermosetting resin compositions that areused in a wide range of fields including electrical and electronicparts, structural materials, adhesives and coating materials, because oftheir manageability and the excellent electrical characteristics, heatresistance, adhesion and humidity resistance (water resistance) of theircured products.

Sealing materials are used in electronic devices to protect theelectronic parts such as semiconductor elements from factors in theexternal environment including impacts, pressure, humidity and heat.Such sealing materials have epoxy resins as the active compounds, andepoxy/phenol-based sealing materials with phenol resin curing agents arewidely used.

Power semiconductors, such as on-vehicle power modules, are electronicdevices considered to be an important key technology for achievingenergy savings in electrical and electronic devices, and there is anincreasing trend toward silicon carbide (SiC), gallium nitride (GaN) anddiamond (C) semiconductors, known as wide band gap semiconductors, thatpromise higher current, smaller sizes and greater efficiency for powersemiconductors, as well as higher efficiency than conventional silicon(Si) semiconductors. The advantage of SiC semiconductors is theirability to operate under higher temperature conditions, and thereforesemiconductor sealing materials must have even higher heat resistancethan currently exhibited.

In the case of power semiconductors with high voltage resistancespecifications, the working voltage may reach from several hundred toseveral thousand volts. Under such high voltage conditions, defects havebeen reported to occur due to the phenomenon of partial discharge.Partial discharge is the phenomenon in which local discharge between anelectrode and an insulator surface (surface corona) or discharge in thegap (void) inside an insulator (void corona) causes corrosion of theinsulator.

With a crosslinkable polymer, higher crosslink density preventsbreakdown caused by electric field-accelerated electrons and helpsminimize formation of fine pores, potentially improving the insulatingproperty. Minimizing formation of fine pores in the cured product in thesteps of resin molding such as transfer molding is also thought toimprove the insulating property.

Materials reported to have excellent heat resistance includeheat-resistant resin compositions comprising maleimide compounds andpolyamines (see PATENT DOCUMENT 1), and bismaleimide resins modifiedwith polybenzoxazine (see PATENT DOCUMENT 2). Such heat-resistant resincompositions, when cured, can exhibit excellent heat resistance.

PRIOR ART DOCUMENTS

PATENT DOCUMENT 1 Japanese Unexamined Patent Publication No. 2014-177584

PATENT DOCUMENT 2 Japanese Unexamined Patent Publication No. 2012-97207

Even when high heat-resistant resins such as those mentioned above areused, however, it has not been possible to obtain sufficient resistancein heat cycle tests with repeated heating/cooling, used to simulate anactual high temperature operation device, and in power cycle tests thatmodel the high-temperature operating state of an element.

SUMMARY OF INVENTION Problems to be Solved by the Invention

The present invention has been accomplished in light of this background,and its object is to provide a curable resin composition that canexhibit sufficient resistance in heat cycle testing and/or power cycletesting, a sealing material using the curable resin composition, asemiconductor device using the sealing material, and a method forproducing the semiconductor device.

Means for Solving the Problems

The present inventors have completed this invention as a result ofdiligent research in light of the circumstances described above.Specifically, the present invention provides the following:

[1]

A resin composition including (A) an epoxy resin, (B) a curing agent and(C) an inorganic filler, and satisfying the following conditions:

(I-I) the minimum modulus is no greater than 10⁴ MPa by evaluation witha rheometer when evaluated at a set temperature of 200° C. aftertemperature increase from 23° C. to 200° C. at 50° C./min, and the finalmodulus is 10⁵ MPa or greater from 10 min after the initial temperatureincrease;

(I-II) the softening point of the epoxy resin (A) is 35° C. or higher;

(I-III) the residual solvent in the resin composition is less than 0.1wt %; and

(I-VI) the equivalent value of the curing agent (B) is no greater than90 g/eq, and the softening point is 105° C. or higher.

[2]

A resin composition including (A) an epoxy resin, (B) a curing agent and(C) an inorganic filler, and satisfying the following conditions:

(II-I) the abundance ratio of C atoms of the epoxy resin (A) or curingagent (B) and X atoms of the inorganic filler (C), based on EDXmeasurement, on the surface of the inorganic filler (C) in the resincomposition, is such that C/X=≥1, where the X atoms are atoms other thanC, O, H or N atoms in the main component of the inorganic filler (C)(the component present in a range of 1 to 95 mol %), and X is defined asthe molar concentration of X atoms;

(II-II) the weight percentage of the inorganic filler (C) in the resincomposition is no greater than 95 wt %;

(II-III) the mean particle size of the inorganic filler (C) is 0.5 μm orgreater;

(II-IV) a ratio of the specific surface area of the inorganic filler (C)for the total resin composition is no greater than 3 m²/g;

(II-V) the softening point of the epoxy resin (A) is 35° C. or higher;

(II-VI) the residual solvent in the resin composition is less than 0.1wt %; and

(II-VII) the equivalent value of the curing agent (B) is no greater than90 g/eq and the softening point is 105° C. or higher.

[3]

A resin composition according to [1] or [2] above, wherein the curingagent (B) is a compound with amino groups.

[4]

A sealing material comprising the cured product of a resin compositionaccording to any one of [1] to [3] above.

[5]

A semiconductor device wherein a semiconductor element is sealed with asealing material according to [4] above.

[6]

A method for producing a semiconductor device, including a step ofsealing a semiconductor element by compression molding using a sealingmaterial according to [4] above.

Effects of the Invention

The resin composition of the invention, when cured, has sufficientchemical heat resistance and crosslink density, and supports adequatemoldability. When it is applied in a transfer molding step, therefore,excessive pressure is less likely to be exerted on elements and wiringsto be sealed, and the sealed elements are less likely to form defects.Moreover, the cured product itself has heat resistance and is resistantto formation of fine pores that can lead to defects during the transfermolding step, and exhibits excellent performance in heat cycle testingand/or power cycle testing.

A sealing material composed of the cured resin composition of theinvention can exhibit its excellent heat resistance. It is thereforesuitable as a sealing material for electronic device products using SiCsubstrates, for example.

Moreover, an electronic device product using the sealing material of theinvention can adequately exhibit the performance of the sealing materialeven under the high operating temperature environment of 200° C., forexample. It can therefore be utilized as an electronic device productwith excellent reliability at high temperature.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a graph showing the relationship between temperature and losselastic modulus, for tablets of the resin compositions obtained inExample 1 and Comparative Example 1.

FIG. 2(2-a) is a surface image taken by scanning electron microscope(SEM) of a tablet of the resin composition obtained in Example 1, FIG.2(2-b) shows the elemental distribution by energy dispersive X-ray (EDX)analysis of the inorganic filler surface (Pt2-1) of the tablet, and FIG.2(2-c) shows the elemental distribution by EDX analysis of the detachedportion (Pt2-2) of the inorganic filler of the tablet.

FIG. 3(3-a) is a surface image taken by SEM of a tablet of the resincomposition obtained in Comparative Example 1, and FIG. 3(3-b) and FIG.3(3-c) show elemental distributions by EDX of the inorganic fillersurfaces (Pt3-1) and (Pt3-2), respectively, of the tablet.

FIG. 4 is a schematic diagram of a power semiconductor device to be usedfor the embodiment.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

The following resin composition may be described as one mode of theinvention. Specifically, it is a resin composition:

including (A) an epoxy resin, (B) a curing agent and (C) an inorganicfiller, and satisfying the following conditions:

(I-I) the minimum modulus is no greater than 10⁴ MPa when evaluated at aset temperature of 200° C. after temperature increase from 23° C. to200° C. at 50° C./min, by evaluation with a rheometer, and the finalmodulus is 10⁵ MPa or greater from 10 min after the initial temperatureincrease;

(I-II) the softening point of the epoxy resin (A) is 35° C. or higher;

(I-III) the residual solvent in the resin composition is less than 0.1wt %; and

(I-IV) the equivalent value of the curing agent is no greater than 90g/eq and the softening point is 105° C. or higher.

The resin composition of the invention, with a minimum modulus valuelimited to no greater than 10⁴ MPa, has a sufficient flowability whenmolding in a transfer molding step, and therefore excess pressure is notexerted on elements and wirings to be sealed, while the cured productalso has heat resistance because of its sufficient crosslink density, sothat sufficient resistance can be obtained in heat cycle testing and/orpower cycle testing. Specifically, by limiting the minimum modulus valueto no greater than 10⁴ MPa, excess pressure is less likely to be exertedon elements and wirings to be sealed, during molding in the transfermolding step, and it is possible to fill the resin into the mold withfewer fine pores being formed in the cured product after sealing,thereby allowing the resistance in heat cycle testing and/or power cycletesting to be increased. If the minimum modulus is higher it will bedifficult to accomplish proper filling, and defects will tend to beproduced during heat cycle testing and/or power cycle testing. If thefinal modulus is 10⁵ MPa or smaller, the curing will be insufficient andproblems may result, such as deformation of the molded article. Bylimiting the softening point of the epoxy resin (A) to 35° C. or higher,it is possible to ensure heat resistance of the cured product and toincrease resistance in heat cycle testing and/or power cycle testing. Ifthe residual solvent in the resin composition is less than 0.1 mass %,this will minimize defects such as swelling caused by the residualsolvent in the transfer molding step, and can increase the resistance inheat cycle testing and/or power cycle testing. In addition, if theequivalent value of the curing agent (B) is no greater than 90 g/eq itwill be possible to ensure the crosslink density and heat resistance ofthe cured product, thereby allowing resistance to be increased in heatcycle testing and/or power cycle testing. Likewise, by limiting thesoftening point of the curing agent (B) to 105° C. or higher, it ispossible to ensure the heat resistance of the cured product and toincrease its resistance in heat cycle testing and/or power cycletesting.

The minimum modulus value according to the invention can be achieved,for example, by adequately covering the inorganic filler (C) with theepoxy resin (A) or curing agent (B), by limiting the weight percentageof the inorganic filler (C) to no greater than 95 wt %, by limiting themean particle size of the inorganic filler (C) to 0.5 μm or greater, orby limiting the specific surface area of the inorganic filler (C) withrespect to the total resin composition to no greater than 3 m²/g.

The heat resistance of the cured product of the invention can beexhibited by adding an epoxy resin (A) with a softening point of 35° C.or higher to the resin composition, or by adding a curing agent (B) withan equivalent value of no greater than 90 g/eq and a softening point of105° C. or higher to the resin composition.

The following resin composition may also be described as one mode of theinvention. Specifically, it is a resin composition including (A) anepoxy resin, (B) a curing agent and (C) an inorganic filler, andsatisfying the following conditions:

(II-I) the abundance ratio of C atoms of the epoxy resin (A) or curingagent (B) and X atoms of the inorganic filler (C), based on EDXmeasurement, on the surface of the inorganic filler (C) in the resincomposition, is such that C/X=≥1

{where the X atoms are atoms other than C, O, H or N atoms in the maincomponent of the inorganic filler (C) (the component present in a rangeof 1 to 95 mol %), and X is defined as the molar concentration of Xatoms};

(II-II) the weight percentage of the inorganic filler (C) in the resincomposition is no greater than 95 wt %;

(II-III) the mean particle size of the inorganic filler (C) is 0.5 μm orgreater;

(II-IV) the specific surface area of the inorganic filler (C) withrespect to the total resin composition is no greater than 3 m²/g;

(II-V) the softening point of the epoxy resin (A) is 35° C. or higher;

(II-VI) the residual solvent in the resin composition is less than 0.1wt %; and

(II-VII) the equivalent value of the curing agent (B) is no greater than90 g/eq and the softening point is 105° C. or higher.

By specifying C/X 1 for the abundance ratio of C atoms of the epoxyresin (A) or the curing agent (B) and X atoms of the inorganic filler(C), the inorganic filler (C) has satisfactory sliding property duringmolding in the transfer molding step, excess pressure is less likely tobe exerted on the elements and wirings to be sealed, and the sealedcured product is less likely to generatefine pores in the cured product,and it is therefore possible to increase the resistance in heat cycletesting and/or power cycle testing. Likewise, by limiting the weightpercentage of the inorganic filler (C) to no greater than 95 wt %, thecomposition in the transfer molding step is has sufficient flowability,and it is possible to increase the moldability and the resistance inheat cycle testing and/or power cycle testing. Likewise, by limiting themean particle size of the inorganic filler (C) to 0.5 μm or greater, theflowability of the composition in the transfer molding step issufficient, and it is possible to increase the moldability and theresistance in heat cycle testing and/or power cycle testing. Moreover,by limiting the specific surface area of the inorganic filler (C) withrespect to the total resin composition to no greater than 3 m²/g, theflowability of the composition in the transfer molding step issufficient, and it is possible to increase the moldability and theresistance in heat cycle testing and/or power cycle testing. If theamount of inorganic filler (C) is too high, the composition in thetransfer molding step will exhibit poor flowability, molding defects maybe generated, and defects will tend to be produced in heat cycle testingand/or power cycle testing. Likewise, if the mean particle size of theinorganic filler (C) is smaller than the range specified above, thecomposition in the transfer molding step will exhibit poor flowability,molding defects may be generated, and defects will tend to be producedin heat cycle testing and/or power cycle testing. Similarly, if thespecific surface area of the inorganic filler (C) with respect to thetotal resin composition is too large, the flowability during transfermolding will become poor, molding defects may be generated, and defectswill tend to be produced in heat cycle testing and/or power cycletesting. By limiting the softening point of the epoxy resin (A) to 35°C. or higher, it is possible to ensure heat resistance of the curedproduct and to increase resistance in heat cycle testing and/or powercycle testing. If the residual solvent in the resin composition is lessthan 0.1 mass %, this will minimize defects such as swelling caused byresidual solvent in the transfer molding step, and can increase theresistance in heat cycle testing and/or power cycle testing. If theequivalent value of the curing agent (B) is no greater than 90 g/eq itwill be possible to ensure crosslink density and heat resistance of thecured product, thereby allowing resistance to be increased in heat cycletesting and/or power cycle testing. Likewise, by limiting the softeningpoint of the curing agent (B) to 105° C. or higher, it is possible toensure heat resistance of the cured product and to increase resistancein heat cycle testing and/or power cycle testing.

The resin composition of the invention includes the epoxy resin (A),curing agent (B) and inorganic filler (C) as essential components, butit may also include other components.

The resin composition of the invention has a minimum modulus ofpreferably no greater than 10⁴ MPa, more preferably no greater than 10³MPa and even more preferably no greater than 10² MPa at 23 to 200° C.before thermosetting treatment. If the modulus value is within thisrange, it will be possible to prevent pressure-induced damage tosemiconductor elements and to element wirings, as well as formation ofvoids in the cured product caused by an insufficient flow propertyduring the transfer molding step.

The modulus after 10 min from the start of temperature increase underthese conditions is preferably 10⁵ MPa or greater, more preferably 10⁶MPa or greater and even more preferably 10⁷ MPa or greater. If themodulus value is within this range, it will be possible to sufficientlycure the resin during molding in the transfer molding step.

The modulus is the value of the loss elastic modulus measured by theparallel plate method using a rheometer (DHR-2 by TA Instruments). Morespecifically, the modulus is measured with a 2000 μm gap, a rotationplate diameter of 8 mm, a frequency of 1.0 Hz, a strain of 0.1%,temperature increase from 23° C. to 200° C. at a rate of 50° C./min andholding at 200° C., by which the minimum modulus and the modulus after10 minutes can be determined.

The components of the resin composition of the invention will now beexplained in detail.

[(A) Epoxy Resin]

The epoxy resin (A) may generally be a monomer, oligomer or polymer withtwo or more epoxy groups per molecule, with no particular restrictionson the molecular weight or molecular structure, and examples includebisphenol-type epoxy resins such as bisphenol A-type epoxy resins,bisphenol F-type epoxy resins and tetramethylbisphenol F-type epoxyresins, biphenyl-type epoxy resins such as biphenyl-type epoxy resinsand tetramethylbiphenyl-type epoxy resins, crystalline epoxy resins suchas stilbene-type epoxy resins and hydroquinone-type epoxy resins;novolac-type epoxy resins such as cresol-novolac-type epoxy resins,phenol-novolac-type epoxy resins and naphthol-novolac-type epoxy resins;phenolaralkyl-type epoxy resins such as phenylene backbone-containingphenolaralkyl-type epoxy resins, biphenylene backbone-containingphenolaralkyl-type epoxy resins, phenylene backbone-containingnaphtholaralkyl-type epoxy resins and alkoxynaphthalenebackbone-containing phenolaralkyl epoxy resins; trifunctional epoxyresins such as triphenolmethane-type epoxy resins and alkyl-modifiedtriphenolmethane-type epoxy resins; modified phenol-type epoxy resinssuch as dicyclopentadiene-modified phenol-type epoxy resins andterpene-modified phenol-type epoxy resins; heterocyclic ring-containingepoxy resins such as triazine nucleus-containing epoxy resins; andphosphorus atom-containing epoxy resins, any one or a combination of twoor more of which may be used.

Preferred among these compounds are triphenolmethane-type epoxy resinssuch as EPPN501H, EPPN501, EPPN501HY, EPPN502 and EPPN502H (product ofNippon Kayaku Co., Ltd.), and dicyclopentadiene types such as XD-1000 2Land XD-1000 (both by Nippon Kayaku Co., Ltd.), and HP-7200 and HP-7200H(both by DIC Corp.).

Phosphorus atom-containing epoxy resins include epoxidated compounds of9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (hereunderabbreviated as “HCA”), epoxidated compounds of phenol resins obtained byreacting HCA with a quinone, epoxy resins that are phenol-novolac-typeepoxy resins modified with HCA, epoxy resins that arecresol-novolac-type epoxy resins modified with HCA, and epoxy resinsobtained by modifying bisphenol A-type epoxy resins with phenol resinsobtained by reacting HCA with a quinone.

The softening point of the epoxy resin (A) is preferably 35° C. orhigher from the viewpoint of heat resistance of the cured product, andit is more preferably 50° C. or higher and even more preferably 60° C.or higher. There is no particular restriction on the upper limit of thesoftening point of the epoxy resin, but it is preferably no higher than130° C. from the viewpoint of ensuring reactivity of the epoxy resin.

The softening point referred to herein can be measured by the ring andball method based on JIS K2351, for example.

The lower limit for the mixing proportion of the total epoxy resin isnot particularly restricted, but it is preferably 5 mass % or greater,more preferably 10 mass % or greater and even more preferably 17 mass %or greater in the total resin composition. If the lower limit of themixing proportion is within this range there will be less risk ofreducing the flow property. The upper limit for the mixing proportion ofthe total epoxy resin is also not particularly restricted, but it ispreferably no greater than 50 mass % and more preferably no greater than40 mass % in the total resin composition. If the upper limit for themixing proportion is within this range, it will be easier to match thecoefficient of thermal expansion with that of the surrounding materials.In order to improve the melt property of the resin, it is preferred toappropriately adjust the mixing proportion according to the type ofepoxy resin used.

[Curing Agent (B)]

The curing agent (B) is not particularly restricted so long as it reactswith the epoxy resin to accomplish curing, and examples include linearaliphatic diamines with 2 to 20 carbon atoms such as ethylenediamine,trimethylenediamine, tetramethylenediamine and hexamethylenediamine, andother amines such as metaphenylenediamine, paraphenylenediamine,paraxylenediamine, 4,4′-diaminodiphenylmethane,4,4′-diaminodiphenylpropane, 4,4′-diaminodiphenyl ether,4,4′-diaminodiphenylsulfone, 4,4′-diaminodicyclohexane,bis(4-aminophenyl)phenylmethane, 1,5-diaminonaphthalene,metaxylenediamine, paraxylenediamine, 1,1-bis(4-aminophenyl)cyclohexaneand dicyanodiamide; resol-type phenol resins such as aniline-modifiedresol resins and dimethyl ether resol resins; novolac-type phenol resinssuch as phenol-novolac resins, cresol-novolac resins,tert-butylphenol-novolac resins and nonylphenol-novolac resins;phenolaralkyl resins such as phenylene backbone-containing phenolaralkylresins and biphenylene backbone-containing phenolaralkyl resins; phenolresins with condensed polycyclic structures such as naphthalenebackbones or anthracene backbones; polyoxystyrenes such aspolyparaoxystyrene; acid anhydrides including alicyclic acid anhydridessuch as hexahydrophthalic anhydride (HHPA) and methyltetrahydrophthalicanhydride (MTHPA) and aromatic acid anhydrides such as trimelliticanhydride (TMA), pyromellitic anhydride (PMDA) andbenzophenonetetracarboxylic acid (BTDA); polymercaptane compounds suchas polysulfides, thioesters and thioethers; isocyanate compounds such asisocyanate prepolymers and blocked isocyanates; and organic acids suchas carboxylic acid-containing polyester resins. These may be used aloneor in combinations of two or more.

The equivalent value of the curing agent is preferably no greater than90 g/eq, more preferably 80 g/eq and even more preferably no greaterthan 70 g/eq, from the viewpoint of heat resistance of the curedproduct. If the equivalent value of the cured product is within thisrange, it will be possible to ensure adequate crosslink density for thecured product and to obtain physical heat resistance.

The equivalent value of the curing agent is defined as the number ofgrams that includes 1 equivalent of active hydrogen in the curing agent.

From the viewpoint of heat resistance of the cured product, thesoftening point of the curing agent is preferably 105° C. or higher,more preferably 140° C. or higher and even more preferably 170° C. orhigher. If the softening point of the curing agent is within this range,the cured product will be able to exhibit chemically adequate heatresistance.

Preferred curing agents include 4,4′-diaminodiphenylsulfone (DDS),3,3′-diaminodiphenylsulfone, 1,3-bis(3-aminophenoxy)benzene, 4,4,4′-diaminodiphenyl ether, 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene,α,α′-bis(4-aminophenyl)-1,4-diisopropylbenzene and paraphenylenediamine.

Also, from the viewpoint of reliability and ensuring crosslink density,the curing agent used in a semiconductor sealing material is preferablyan amine-based or amino-based compound, and more preferably at least onediamine compound selected from the group consisting of aromatic diaminecompounds, aromatic bisaminophenol compounds, alicyclic diamines,straight-chain aliphatic diamines and siloxanediamines.

Aromatic bisaminophenol compounds include 3,3′-dihydroxybenzidine,3,3′-diamino-4,4′-dihydroxybiphenyl,3,3′-dihydroxy-4,4′-diaminodiphenylsulfone,bis-(3-amino-4-hydroxyphenyl)methane,2,2-bis-(3-amino-4-hydroxyphenyl)propane,2,2-bis-(3-amino-4-hydroxyphenyl)hexafluoropropane,2,2-bis-(3-hydroxy-4-aminophenyl)hexafluoropropane,bis-(3-hydroxy-4-aminophenyl)methane,2,2-bis-(3-hydroxy-4-aminophenyl)propane,3,3′-dihydroxy-4,4′-diaminobenzophenone,3,3′-dihydroxy-4,4′-diaminodiphenyl ether,4,4′-dihydroxy-3,3′-diaminodiphenyl ether,2,5-dihydroxy-1,4-diaminobenzene, 4,6-diaminoresorcinol,1,1-bis(3-amino-4-hydroxyphenyl)cyclohexane and4,4-(α-methylbenzylidene)-bis(2-aminophenol).

Alicyclic diamine compounds include 1,3-diaminocyclopentane,1,3-diaminocyclohexane, 1,3-diamino-1-methylcyclohexane,3,5-diamino-1,1-dimethylcyclohexane,1,5-diamino-1,3-dimethylcyclohexane,1,3-diamino-1-methyl-4-isopropylcyclohexane,1,2-diamino-4-methylcyclohexane, 1,4-diaminocyclohexane,1,4-diamino-2,5-diethylcyclohexane, 1,3-bis(aminomethyl)cyclohexane,1,4-bis(aminomethyl)cyclohexane, 2-(3-aminocyclopentyl)-2-propylamine,mensen*diamine, isophorone diamine, norbornanediamine,1-cycloheptene-3,7-diamine, 4,4′-methylenebis(cyclohexylamine),4,4′-methylenebis(2-methylcyclohexylamine),1,4-bis(3-aminopropyl)piperazine and3,9-bis(3-aminopropyl)-2,4,8,10-tetraoxaspiro-[5,5]-undecane.

Straight-chain aliphatic diamine compounds include hydrocarbon-typediamines such as 1,2-diaminoethane, 1,4-diaminobutane,1,6-diaminohexane, 1,8-diaminooctane, 1,10-diaminodecane and1,12-diaminododecane, and alkylene oxide-type diamines such as2-(2-aminoethoxy)ethylamine, 2,2′-(ethylenedioxy)diethylamine andbis[2-(2-aminoethoxy)ethyl]ether.

Siloxanediamine compounds include dimethyl (poly)siloxanediamine, suchas PAM-E, KF-8010 and X-22-161A which are trademarks of Shin-EtsuChemical Co., Ltd.

When the curing agent is to be used, the mixing ratio of the total epoxyresin with the total curing agent is preferably between 0.8 and 1.3,inclusive, as the equivalent ratio of the number of epoxy groups (EP) ofthe total epoxy resin and the equivalent value of the total curingagent. If the equivalent ratio is within this range, it is possible toobtain sufficient curability during molding of the resin composition.Moreover, if the equivalent ratio is within this range it is possible toobtain satisfactory physical properties for the cured resin. Inconsideration of heat resistance of the resin composition, theequivalent ratio is preferably close to 1.0 to allow increase in thecurability of the resin composition and the glass transition temperatureor heated elastic modulus of the cured resin.

[Inorganic Filler (C)]

The inorganic filler (C) is not particularly restricted so long as ithas a satisfactory melt property in the resin composition of theinvention, and examples include silica such as molten crushed silica,molten spherical silica, crystalline silica and two-dimensionalaggregated silica, and alumina, silicon nitride, aluminum nitride, boronnitride, titanium oxide, silicon carbide, aluminum hydroxide, magnesiumhydroxide, titanium white, talc, clay, mica, glass fiber and the like.Molten spherical silica is particularly preferred among those mentionedabove. The particle shapes are preferably as spherical as possible, andthe filling volume can be increased by mixing particles of differentsizes. In order to increase the melt property of the resin composition,it is preferred to use molten spherical silica.

The upper limit for the content ratio of the inorganic filler (C) ispreferably no greater than 95 mass %, more preferably no greater than 90mass % and even more preferably no greater than 83 mass %, based on thetotal epoxy resin composition for sealing according to the invention. Ifthe upper limit for the content ratio of the inorganic filler is withinthis range, it will be possible to obtain satisfactory results in heatcycle testing after curing, without decreasing flowability of the resincomposition. The lower limit for the content ratio of the inorganicfiller is not particularly restricted, but it is preferably 50 mass % orgreater and more preferably 60 mass % or greater in the total resincomposition. If the upper limit for the mixing proportion is within thisrange, it will be easier to match the coefficient of thermal expansionwith that of the surrounding members.

The lower limit for the mean particle size (D50) of the inorganic filler(C) is preferably 0.5 μm or greater, more preferably 1 μm or greater andeven more preferably 4 μm or greater. There is no particular restrictionon the upper limit for the mean particle size of the inorganic filler,but it is preferably no greater than 50 μm and even more preferably nogreater than 40 μm. Also, the maximum particle size is preferably nogreater than 105 μm. If the mean particle size is less than 0.5 μm, theflowability of the resin composition will be decreased, potentiallyimpairing the moldability. If the mean particle size is greater than 40μm, on the other hand, warping of the molded article may occur, and thedimensional precision can potentially be lowered. If the maximumparticle size is greater than 105 μm, the moldability may be reduced.

The mean particle size (D50) of the inorganic filler (C) referred toherein can be determined as follows: with a laser diffraction particlesize distribution analyzer (Helos & Rodos by Sympatec), the meanparticle size being the particle size (D50) at which the cumulativevolume is 50% in the particle size distribution was measured with thesame analyzer.

The inorganic filler used may consist of two or more inorganic fillerswith different specific surface areas (SSA) and/or mean particle sizes(D50).

The inorganic filler (C) may be a single type or a mixture of two ormore types, and the specific surface area (SSA) with respect to thetotal (D) composition is preferably no greater than 3 m²/g, morepreferably no greater than 2.5 m²/g and even more preferably no greaterthan 2 m²/g. If the specific surface area (SSA) with respect to thetotal composition is within this range, it will be easier to ensure theflowability of the resin composition.

The specific surface area (SSA) of the inorganic filler (C) referred toherein can be determined, for example, by the BET method using aspecific surface area meter.

The specific surface area (SSA) of the inorganic filler (C) with respectto the total (D) composition, as referred to herein, can be determined,for example, by the following formula:Specific surface area (SSA) with respect to total composition=A×X+B×Y,when using a mixture of two different inorganic fillers, an inorganicfiller with the specific surface area A m²/g and the amount X wt %, andan inorganic filler with the specific surface area B m²/g and the amountY wt %.

If necessary, a curing accelerator may be mixed with the resincomposition of the invention, in addition to the components mentionedabove. The curing accelerator may be any one that accelerates the curingreaction between the epoxy groups and the curing agent, and it may beone generally used for sealing materials. Specific examples includeorganic phosphorus atom-containing compounds such as organic phosphines,tetra-substituted phosphonium compounds, phosphobetaine compounds,addition products of phosphine compounds and quinone compounds andaddition products of phosphonium compounds and silane compounds;amidine-based compounds such as 1,8-diazabicyclo(5,4,0)undecene-7 andimidazole; nitrogen atom-containing compounds, representative of whichare tertiary amines such as benzyldimethylamine or amidinium salts thatare quaternary onium salts, ammonium salts, or amine complex salts ofthe aforementioned compounds, and boron compounds, organic acid metalsalts, Lewis acids and the like.

The lower limit for the mixing proportion of the total curingaccelerator is also not particularly restricted, but it is preferably0.1 mass % or greater in the total resin composition. If the lower limitfor the mixing proportion of the total curing accelerator is within thisrange, it will be possible to obtain sufficient curability. The upperlimit for the mixing proportion of the total curing accelerator is alsonot particularly restricted, but it is preferably no greater than 1 mass% in the total resin composition. If the upper limit for the mixingproportion of the total curing accelerator is within this range, it willbe possible to obtain a sufficient flow property. In order to improvethe melt property of the resin, it is preferred to appropriately adjustthe mixing proportion according to the type of curing accelerator used.

If necessary, a coupling agent may be mixed with the resin compositionof the invention, in addition to the components mentioned above. Thecoupling agent used may be any of the publicly known coupling agentsthat include silane-based compounds such as epoxysilane, mercaptosilane,aminosilane, alkylsilane, ureidosilane and vinylsilane, titanium-basedcompounds, aluminum chelates and aluminum/zirconium-based compounds.Examples thereof include silane-based coupling agents such asvinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane,vinyltris(β-methoxyethoxy)silane, γ-methacryloxypropyltrimethoxysilane,β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane,γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane,γ-glycidoxypropylmethyldimethoxysilane,γ-methacryloxypropylmethyldiethoxysilane,γ-methacryloxypropyltriethoxysilanevinyltriacetoxysilane,γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane,γ-anilinopropyltrimethoxysilane, γ-anilinopropylmethyldimethoxysilane,γ-[bis(β-hydroxyethyl)]aminopropyltriethoxysilane,N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane,N-β-(aminoethyl)-γ-aminopropyltriethoxysilane,N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane,N-phenyl-γ-aminopropyltrimethoxysilane,γ-(β-aminoethyl)aminopropyldimethoxymethylsilane,N-(trimethoxysilylpropyl)ethylenediamine,N-(dimethoxymethylsilylisopropyl)ethylenediamine,methyltrimethoxysilane, dimethyldimethoxysilane, methyltriethoxysilane,N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane,γ-chloropropyltrimethoxysilane, hexamethyldisilane,vinyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane,3-isocyanatepropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane and3-triethoxylyl-N-(1,3-dimethyl-butylidene)propylamine hydrolysate, andtitanate-based coupling agents such as isopropyltriisostearoyl titanate,isopropyltris(dioctyl pyrophosphate) titanate,isopropyltri(N-aminoethyl-aminoethyl)titanate, tetraoctylbis(ditridecylphosphite) titanate,tetra(2,2-diallyloxymethyl-1-butyl)bis(ditridecyl)phosphite titanate,bis(dioctyl pyrophosphate)oxyacetate titanate, bis(dioctylpyrophosphate)ethylene titanate, isopropyltrioctanoyl titanate,isopropyldimethacrylisostearoyl titanate,isopropyltridodecylbenzenesulfonyl titanate, isopropylisostearoyldiacryltitanate, isopropyltri(dioctyl phosphate) titanate,isopropyltricumylphenyl titanate and tetraisopropylbis(dioctylphosphite) titanate, any of which may be used alone or in combinationsof two or more.

There are no particular restrictions on the amount of coupling agentadded, but it is preferably between 0.05 mass % and 3 mass %, inclusiveand more preferably between 0.1 mass % and 2.5 mass %, inclusive, withrespect to the inorganic filler (C). An amount of 0.05 mass % or greaterwill allow satisfactory frame adhesion, and an amount of up to 3 mass %can improve the moldability.

If necessary, known additives may be mixed with the resin composition ofthe invention, in addition to the components mentioned above. Specificexamples of additives that may be used include coloring agents such ascarbon black and titanium oxide; release agents such as natural waxes,synthetic waxes, higher fatty acids or their metal salts, paraffin,aliphatic esters and polyethylene oxide; low stress agents such assilicone oil, silicone rubber and olefin rubber; ion scavengers such ashydrotalcite; flame retardants, including inorganic flame retardantssuch as aluminum hydroxide and antimony trioxide, phosphorus-based flameretardants, nitrogen-based flame retardants, silicone-based flameretardants and organometallic salt-based flame retardants; and otheradditives such as antioxidants, curing aids, emulsifiers and the like.

The resin composition of the invention will usually be in the form ofpowder, or molded tablets as necessary, and it can be produced using anymethod known in the prior art that allows the various components to beuniformly dispersed and mixed. For example, all of the components may bepulverized and mixed with a Henschel mixer or the like, and then thecomposition prepared by melt kneading with a heated roll, melt kneadingwith a kneader, mixing with a special mixer, or an appropriatecombination of these methods. Also, the semiconductor device of theinvention may be produced by the resin-sealed semiconductor elementsmounted on a lead frame or the like, by transfer molding using the resincomposition of the invention.

A solvent may be used for preparation of the resin composition, but inlight of concerns regarding generation of voids by the solvent in thecured product, or poor appearance or reduced reliability, preparationwill usually be performed in a solventless condition.

The residual solvent in the resin composition is preferably no greaterthan 0.1 wt %, more preferably no greater than 0.05 wt % and even morepreferably no greater than 0.01 wt %. The residual solvent can bequantified by gas chromatography, for example.

The resin composition of the invention can exhibit a higher flowabilityby having the inorganic filler (C) surface sufficiently covered by theepoxy resin (A) and curing agent (B), in powdered form or as moldedtablets.

The abundance ratio of C atoms of the epoxy resin (A) component orcuring agent (B) component and X atoms of the inorganic filler (C)component on the surface of the inorganic filler (C) component beforethermosetting treatment, as measured by EDX, is preferably C/X=≥1, morepreferably C/X=≥1.5 and even more preferably C/X=≥2. If the value of C/Xis within this range, the resin composition can exhibit an even higherflowability. The X atoms are atoms other than C, O, H or N atoms in themain component of the inorganic filler (C) component (defined as thecomponent present in a range of 1 to 95 mol %), and X is defined as themolar concentration of X atoms of the main component. The type of X atomis not particularly restricted, but it is preferably a light element,light metal or metal. The X atom will differ depending on the type ofinorganic filler, and it will be an Al atom in the case of alumina, a Batom in the case of boron nitride, a Mg atom in the case of magnesiumhydroxide and a Si atom in the case of silica.

Incidentally, C is the molar concentration of carbon atoms in the epoxyresin (A) component or curing agent (B) component, and the maincomponent of the inorganic filler (C) component is the component presentat 1 to 95 mol % in the inorganic filler.

The C/X ratio can be measured, for example, by quantifying the elementsby SEM-EDX, and calculating the compensation for each element from thepeak integral, by a standardless method.

EXAMPLES

The invention will now be explained in greater detail based on examplesand comparative examples. However, the invention is in no way limited bythese examples.

The components used in the examples and comparative examples were thefollowing.

(Epoxy Resin (A))

Epoxy resin 1: Trisphenolmethane-type epoxy resin with a softening pointof 67° C. (EPPN-502H by Nippon Kayaku Co., Ltd.).

Epoxy resin 2: Trisphenolmethane-type epoxy resin with a softening pointof 52° C. (EPPN-501H by Nippon Kayaku Co., Ltd.).

Epoxy resin 3: Dicyclopentadiene-modified epoxy resin with a softeningpoint of 73° C. (XD-1000 by Nippon Kayaku Co., Ltd.).

Epoxy resin 4: Liquid triglycidylaminophenol at room temperature(approximately 23° C.) (JER630 by Mitsubishi Chemical Corp.).

(Curing Agent (B))

Curing agent 1: 62.1 g/eq 4,4′-diaminodiphenylsulfone (DDS) with asoftening point of 175° C. to 180° C. (Wako Pure Chemical Industries,Ltd.).

Curing agent 2: 105 g/eq novolac-type phenol resin with a softeningpoint of 100° C. (RESITOP PSM-4324 by Gun Ei Chemical Industry Co.,Ltd.).

Curing agent 3: 73 g/eq 1,3-bis(3-aminophenoxy)benzene with a softeningpoint of 106.5 to 110° C. (Wako Pure Chemical Industries, Ltd.).

Curing agent 4: 50.6 g/eq 4,4′-diaminodiphenyl ether with a softeningpoint of 186° C. to 187° C. (Wako Pure Chemical Industries, Ltd.).

Curing agent 5: 86.1 g/eq 1,3-bis[2-(4-aminophenyl)-2-propyl]benzenewith a softening point of 115° C. (Tokyo Chemical Industry Co., Ltd.).

Curing agent 6: 86.1 g/eq α,α′-bis(4-aminophenyl)-1,4-diisopropylbenzenewith a softening point of 165° C. (Tokyo Chemical Industry Co., Ltd.).

(Inorganic Filler (C))

Spherical inorganic filler 1: Spherical molten silica (mean particlesize: 32 μm, specific surface area: 1.3 m²/g).

Spherical inorganic filler 2: Spherical molten silica (mean particlesize: 4.2 μm, specific surface area: 1.5 m²/g).

Spherical inorganic filler 3: Spherical molten silica (mean particlesize: 4.2 μm, specific surface area: 3.5 m²/g).

Spherical inorganic filler 4: Spherical molten silica (mean particlesize: 4.2 μm, specific surface area: 4.5 m²/g).

Spherical inorganic filler 5: Spherical molten silica (mean particlesize: 2.7 μm, specific surface area: 2.1 m²/g).

Spherical inorganic filler 6: Spherical molten silica (mean particlesize: 0.4 μm, specific surface area: 7.3 m²/g).

(Other Components)

Curing accelerator: Triphenylphosphine (Tokyo Chemical Industry Co.,Ltd.).

MEK (Wako Pure Chemical Industries, Ltd.)

Examples 1 to 6 and Comparative Examples 2, 3, 5 and 6

A starting material for a resin composition with the composition shownin Table 1 was pulverized and mixed for 5 minutes using a Super Mixer,and then a mixing roll was used for uniform mixing and kneading toobtain epoxy resin compositions for the invention and for comparison.The resin composition for sealing was pulverized with a mixer andtableted with a tableting machine. The residual solvent of thecomposition was quantified by gas chromatography (Shimadzu, GC-2014).

The modulus was measured according to the following method. The resincomposition tableted to 1 cmϕ, 2 mm thickness under a pressure of 20 MPawas measured by the parallel plate method using a rheometer (DHR-2 by TAInstruments). After stabilization to a temperature of 23° C. at the siteof measurement, under conditions with a 2000 μm gap, a rotation platediameter of 8 mm, a frequency of 1.0 Hz and a strain of 0.1%, thetemperature was increased from 23° C. to 200° C. at a rate of 50° C./minand held at 200° C., and the modulus was measured in that range,recording the minimum modulus for the loss elastic modulus and themodulus 10 minutes after initial temperature increase. FIG. 1 shows therheometer results for Example 1 and Comparative Example 1, as anexample. Based on FIG. 1, the value of the minimum modulus wasdetermined to be 1.0×10² MPa in Example 1 and 2.0×10⁴ MPa in ComparativeExample 1, and the modulus after 10 minutes was determined to be 1.0×10⁷MPa in Example 1 and 2.0×10⁷ MPa in Comparative Example 1.

The C/Si ratio was measured by the following method. The resincomposition tableted to 1 cmϕ and a thickness of 1 cm under a pressureof 20 MPa was split open at ordinary temperature, to prepare a splitcross-section of the interior of the sample. After fixing it to a SEMsample stage, it was subjected to conductive treatment for use as asample for microscopy. Using an ultrahigh-resolution field emissionscanning electron microscope (SU8220 by Hitachi High-Technologies Corp.)as SEM and an energy dispersive X-ray analyzer (NORAN System Seven byThermo Fisher Scientific Inc.) as EDX, under conditions with anacceleration voltage of 5 kV, high probe current, a WD (workingdistance) of 15 mm, EDX measuring mode, and an area analysis region ofapproximately 10 μm, the inorganic filler surface of the activecross-section was set as the target with a measuring time of 60 seconds.Compensation for the quantified value for the element was calculated foreach element from the peak integral, using a standardless method. Anexample of the results for Example 1 is shown in FIG. 2 and Table 7, andan example of the results for Comparative Example 1 is shown in FIG. 3and Table 8. Judging from the shaded portions of the SEM photograph, andthe EDX results, it was confirmed that Pt2-1 in FIG. 2 and Table 7 isthe inorganic filler surface and Pt2-2 is a trace of the detachedinorganic filler. Focusing on the results of EDX in FIG. 2 and Table 7,a Si peak attributable to the inorganic filler was observed for Pt2-1since it was the inorganic filler surface, while virtually no Si peakattributable to the inorganic filler was observed for Pt2-2, as it was atrace of the detached inorganic filler.

A module with a power semiconductor element mounted on it was fabricatedby a common method. The tableted resin composition was used to cover theentire preliminary module by transfer molding, and subjected to heatcuring at 250° C. for 8 hours to fabricate a resin-sealed powersemiconductor device.

A schematic diagram of the fabricated power semiconductor device isshown in FIG. 4. In the power semiconductor device 4, the lower sideelectrode of the power semiconductor element 41 was electricallyconnected to a lead part 43 via a joining material 42. The mainelectrode of the power semiconductor element 41 was electricallyconnected to the lead part 43 via a wire 44. The lower side of the leadpart 43 had a radiator plate 46 provided through a heat transfer sheet45, for outward escape of heat generated by the power semiconductorelement 41. Portions of the lead part 43 and radiator plate 46 were eachexposed while sealing the periphery of the power semiconductor element41 with a sealing material 47. The sealing material 47 includes a resincomposition prepared by the procedure described above.

Each fabricated power semiconductor device was used, for evaluation ofthe cycle life of the power semiconductor devices for Examples 1 to 6and Comparative Examples 1 to 6 by power cycle testing (ΔTc=125° C., 75°C. to 200° C.)

Comparative Example 1

Comparative Example 1 shown in Table 1 was carried out by the samemethod as Example 1, except that after pulverizing and mixing for 5minutes with a super mixer, the mixture was further pulverized and mixedfor 25 minutes with a super mixer, without uniform mixing and kneadingwith a mixing roll.

Comparative Example 4

Comparative Example 4 shown in Table 1 was carried out by the samemethod as Example 1, except that the inorganic filler was treatedbeforehand with MEK as an organic solvent by the method described inInternational Patent Publication No. 2015-125760.

The results are shown in Table 1. A distinct difference was seen betweenthe power cycle test results for Examples 1 to 6 and ComparativeExamples 1 to 6. Since a different mixing method was used in ComparativeExample 1, since the weight fraction of the inorganic filler was toohigh in Comparative Example 2, since the specific surface area of theinorganic filler was too high with respect to the composition inComparative Example 3, and since the particle size of the inorganicfiller was too small in Comparative Example 4, the inorganic fillersfailed to be sufficiently covered with the resin components, andconsequently defects tended to be produced in the power cycle test. InComparative Example 5, curing of the composition was incomplete asindicated by the modulus value after 10 minutes, and consequentlydefects were likely to be produced in the power cycle test. InComparative Example 6, the presence of the solvent in the compositionprobably resulted in defects in the cured product, and consequentlydefects were likely to be produced in the power cycle test.

TABLE 1 Examples Comparative Examples 1 2 3 4 5 6 1 2 3 4 5 6Composition Epoxy resin Epoxy 22 13 7 22 22 22 22 4 22 22 19 22 (A)resin 1 Curing Curing 8 4 3 8 8 8 8 1 8 8 — 8 agent agent 1 (B) Curing —— — — — — — — — — 11 — agent 2 Inorganic Inorganic 70 83 63 — — — 70 67— — 70 70 filler (C) filler 1 Inorganic — — 27 70 — — — 29 — — — —filler 2 Inorganic — — — — 70 — — — — — — — filler 3 Inorganic — — — — —— — — 70 — — — filler 4 Inorganic — — — — — 70 — — — — — — filler 5Inorganic — — — — — — — — — 70 — — filler 6 Solvent MEK — — — — — — — —— — — 0.1 Total 100 100 100 100 100 100 100 100 100 100 100 100Inorganic filler weight fraction [wt %] 70 83 90 70 70 70 70 96 70 70 7070 Specific surface area of inorganic 0.9 1.1 1.2 0.9 2.4 1.5 0.9 1.33.2 4.9 0.9 0.9 filler in composition (m²/g) Solvent content (wt %) 0 00 0 0 0 0 0 0 0 0 0.1 Physical Rheological Minimum 1.0E+02 2.0E+026.0E+02 2.0E+02 1.0E+03 7.0E+02 2.0E+04 2.0E+05 1.0E+05 1.0E+05 1.0E+021.0E+02 properties properties modulus [MPa] Modulus 1.0E+07 1.0E+061.0E+06 1.0E+06 1.0E+06 1.0E+06 1.0E+07 1.0E+06 1.0E+06 1.0E+06 1.0E+021.0E−07 after 10 min [MPa] Inorganic (EDX: C/Si) 2.0 2.0 1.0 2.0 1.0 1.00.3 0.3 0.3 0.3 2.0 2.0 filler coverage Epoxy resin ° C. 67 67 67 67 6767 67 67 67 67 67 67 softening point Evaluation Power cycle test resultsA B C B C B E E D D E E results

TABLE 2 Power cycle 200° C.−75° C. 50,000 cycles 5/5 completed: A4/5-3/5 completed: B 2/5-1/5 completed: C 0/5 completed: D Defects atstart: E

Examples 7 and 8, Comparative Example 7

Example 1, Examples 7 and 8 and Comparative Example 7 shown in Table 3were carried out by the same method as Example 1, except that a heatcycle test was performed at 200° C. to −50° C. instead of the powercycle test of Example 1. The details regarding the heat cycle test areas follows.

Using a TSE-11 heat shock apparatus by Espec Corp., with one cycleconsisting of holding the sample at 200° C. for 30 minutes and at −50°C. for 30 minutes, 500 cycles were conducted and the sample was thenremoved and visual confirmation made of any cracking or peeling in thecured product (Table 4).

The results are shown in Table 3. In Examples 1, 7 and 8, no crackingwas observed after the heat cycle test, but cracking was observed in theheat cycle test in Comparative Example 7. The tendency that defects weregenerated in the heat cycle test in Comparative Example 7 was presumablybecause the softening point of the epoxy resin was too low.

TABLE 3 Examples Comp. 1 7 8 7 Composition Epoxy resin Epoxy resin 1 22— — — (A) Epoxy resin 2 — 22 — — Epoxy resin 3 — — 24 — Epoxy resin 4 —— — 18 Curing agent Curing agent 1 8 8 6 12 (B) Inorganic Inorganic 7070 70 70 filler (C) filler 1 Solvent MEK — — — — Total 100 100 100 100Inorganic filler weight fraction [wt %] 70 70 70 70 Specific surfacearea of inorganic 0.9 0.9 0.9 0.9 filler in composition (m²/g) Solventcontent (wt %) 0 0 0 0 Physical Rheological Minimum 1.0E+02 1.0E+021.0E+02 1.0E+02 properties properties modulus [MPa] Modulus after1.0E+07 1.0E+06 1.0E+06 1.0E+05 10 min [MPa] Inorganic (EDX: C/Si) 2.01.0 2.0 2.0 filler coverage Epoxy resin ° C. 67 50 73 ≤RT softeningpoint Evaluation Heat cycle test results A A A B results

TABLE 4 Temperature cycle 200° C., −50° C. 30 min−30 min, 500 cycles 5/5no outer appearance abnormalities: A Partial cracking: B

Examples 9 to 12, Comparative Example 8

Example 1, Examples 9 to 12 and Comparative Example 8 shown in Table 5were performed by the same method as Table 3, except that thetemperature conditions for the heat cycle test were 180° C. to −50° C.(Table 6).

The results are shown in Table 5. In Examples 1 and 9 to 12, no crackingwas observed after the heat cycle test, but cracking was observed in theheat cycle test in Comparative Example 8. In Comparative Example 8, theheat resistance of the cured product was insufficient due to the lowsoftening point of the curing agent and the crosslink density of thecured product was insufficient due to the excessively large equivalentvalue of the curing agent, and presumably for these reasons, defectswere likely to be produced in the heat cycle test.

TABLE 5 Comp. Examples Example 1 9 10 11 12 8 Composition Epoxy resinEpoxy resin 1 22 21 23 20 20 19 (A) Curing agent Curing agent 1 8 — — —— — (B) Curing agent 2 — — — — — 11 Curing agent 3 — 9 — — — — Curingagent 4 — — 7 — — — Curing agent 5 — — — 10 — — Curing agent 6 — — — —10 — Curing Curing accelerator accelerator 1 — — — — — 0.2 InorganicInorganic 70 70 70 70 70 70 filler (C) filler 1 Total 100 100 100 100100 100 Inorganic filler weight fraction [wt %] 70 70 70 70 70 70Specific surface area of inorganic 0.9 0.9 0.9 0.9 0.9 0.9 filler incomposition (m²/g) Solvent content (wt %) 0 0 0 0 0 0 PhysicalRheological Minimum 1.0E+02 1.0E+02 1.0E+02 1.0E+02 1.0E+02 1.0E102properties properties modulus [MPa] Modulus after 1.0E+07 1.0E+061.0E+06 1.0E+06 1.0E+06 1.0E+05 10 min [MPa] Inorganic (EDX: C/Si) 2.02.0 2.0 2.0 2.0 2.0 filler coverage Epoxy resin ° C. 67 67 67 67 67 67softening point Evaluation Heat cycle test results A A A A A B results

TABLE 6 Temperature cycle 180° C., −50° C. 30 min−30 min, 500 cycles 5/5no outer appearance abnormalities: A Partial cracking: B

TABLE 7 Measured location Pt2-1 Pt2-2 C 37 84 Si 18  1 C/Si 2 —

The quantitative element values are the values compensated for eachelement from the peak integrals in the EDX charts shown in FIG. 2(2-b)and FIG. 2(2-c), using a standardless method.

TABLE 8 Measured location Pt3-1 Pt3-2 C 6 7 Si 26 29 C/Si 0.2 0.2

The quantitative element values are the values compensated for eachelement from the peak integrals in the EDX charts shown in FIG. 3(3-b)and FIG. 3(3-c), using a standardless method.

Based on these results, the power semiconductor devices sealed withsealing materials using resin compositions of the invention exhibitedexcellent power cycle test resistance and heat cycle test resistance.

INDUSTRIAL APPLICABILITY

A sealing material using a resin composition of the invention can beused in a wide range of electrical and electronic fields includingsemiconductor sealing materials and insulating materials for printedcircuit boards. In electrical and electronic fields, highly reliableelectronic devices can be realized when the sealing material is used ina power semiconductor, such as an on-vehicle power module, for example,that is intended to be applied under higher temperature conditions.

BRIEF DESCRIPTION OF THE REFERENCE SYMBOLS

4 Power semiconductor device

41 Power semiconductor element

42 Joining material

43 Lead part

44 Wire

45 Heat transfer sheet

46 Radiator plate

47 Sealing material

The invention claimed is:
 1. A resin composition including (A) an epoxyresin, (B) a curing agent and (C) an inorganic filler, and satisfyingthe following conditions: (II-I) X atoms other than C, O, H and N atomsin the main component of the inorganic filler (C) (the component presentin a range of 1 to 95 mol %), based on EDX measurement, are on thesurface of the inorganic filler (C) in the resin composition; (II-II)the weight percentage of the inorganic filler (C) in the resincomposition is no greater than 95 wt %; (II-III) the mean particle sizeof the inorganic filler (C) is 0.5 μm or greater; (II-IV) a ratio of thespecific surface area of the inorganic filler (C) with respect to thetotal resin composition is no greater than 2 m²/g; (II-V) the softeningpoint of the epoxy resin (A) is 35° C. or higher; (II-VI) the residualsolvent in the resin composition is less than 0.1 wt %; and (II-VII) thesoftening point of the curing agent (B) is 105° C. or higher; andwherein, under the condition (II-I), the abundance ratio of C atoms ofthe epoxy resin (A) or curing agent (B) and the X atoms of the inorganicfiller (C), based on EDX measurement, on the surface of the inorganicfiller (C) in the resin composition satisfies the following formula:C/X =>1 wherein C is defined as a molar concentration of the C atoms andX is defined as a molar concentration of the X atoms.
 2. The resincomposition according to claim 1, wherein, under the condition (II-VII),the equivalent value of the curing agent (B) is no greater than 90 g/eqand the softening point is 105° C. or higher.
 3. A resin compositionaccording to claim 1, wherein the curing agent (B) is a compound withamino groups.
 4. A sealing material comprising the cured product of aresin composition according to claim
 1. 5. A semiconductor devicewherein a semiconductor element is sealed with a sealing materialaccording to claim
 4. 6. A method for producing a semiconductor device,including a step of sealing a semiconductor element by compressionmolding using a sealing material according to claim 4.